Solving a genetic mystery 2

Yesterday, Virga, the leader of the Vuduri on Helome was on her way to take Rome and Rei to see Bonnie Mullen when she stopped at a science lab. She asked Rome and Rei if they might be able to help her clear up a mystery. Our heroes agreed as long as it did not take too much time:

     Virga led them through the front entrance and up one flight of stairs until they came to a large room, set up somewhat like a classroom but with a variety of scientific equipment along the far wall. There was a long table in the front. Virga indicated the seats on the near side. Rei and Rome sat down. Virga closed her eyes and a projector, hidden in the ceiling, lit up the front wall and displayed a map of the human genome. Rei quickly counted 22 pairs of chromosomes plus one X and one Y chromosome; 23 chromosome pairs in all.
     “This is the chromosomal layout of a normal 23-chromosome male mandasurte,” Virga said. She blinked and all but the X and Y chromosomes disappeared. They nestled themselves in the upper left hand corner of the screen. Below them, a second partial map appeared. This one had two X chromosomes plus two additional pairs of chromosomes to the right of the double Xs.
     “This is a normal, full-blooded, Vuduri female with 24 pairs of chromosomes. In fact, this is me.” She turned to face Rome. “As you are aware, the 24th chromosome does not split during meiosis. Propagation of the 24th chromosome is mitotic so a normal Vuduri couple would each require a diploid complement to produce full-blooded children.”
     Virga turned back to the screen. This time, the additional chromosomes slid to the upper right hand corner of the screen and another map appeared. This one had extra pair of chromosomes, even shorter and stubbier than the Y chromosome lined up to the right.
     “20% of the Essessoni that you sent us have the exact genetic complement we expected. They are identical in every way to a 23-chromosome mandasurte. But the other 80% have this extra chromosome pair, a portion of which is reminiscent of our 24th, but they are not DNA in the truest sense. They are a form of peptide nucleic acid and they do not have telomeres on one end. They are quite odd. We call them the 25th chromosome for lack of a better name.”
     “Uh,” Rei started to speak. Rome interrupted him.
     “What is the significance of this?” Rome asked.
     “The significance is this: this genetic material, this extra pair, would prevent the expression of the Onsira phenotype, even in a full-blooded diploid Vuduri. If we could figure out a way to introduce it to the Vuduri population in general, no Onsira would ever be born again. Mosdurece or not.”
     “If this is the case, why have you not done so already?” Rome asked.
     “We have tried,” Virga said, sighing. The projector shut off. “However, we cannot keep the genetic material from disintegrating outside of the cell wall. In other words, we cannot figure out a delivery system.”

So how did it get there in the first place? Rei certainly knows the answer. I guess it is time to come clean.